Varian Associates, Inc.

Other

Varian Medical Systems, Inc.

Eiji Tanabe

Victor A Vaguine

David H Whittum

Mark E Trail

Gard Meddaugh

Matthew Bayer

An energy switch for use in a radiation system includes an element located within a structure having a cavity, the element capable of being biased by a magnetic field, and a device for generating the magnetic field to thereby bias the element. An energy switch for use in a radiation system includes a structure forming at least a part of a cavity, an element coupled to the structure and located outside the cavity, the element capable of being biased by a magnetic field, and a device for generating the magnetic field to bias the element. A method for use in a radiation procedure includes providing a first magnetic field, and using the first magnetic field to create a first bias for an element that is located outside a cavity of an accelerator, thereby changing en electric field associated with the accelerator.

Electronic energy switch

A standing wave accelerator structure that has both inline coupling cavities and side coupling cavities combined into one structure. Additionally, the invention uses a prebunching (re-entrant) cavity, excited electrically or magnetically, through apertures between a first accelerating cavity and the prebunching cavity.

High gradient, compact, standing wave linear accelerator structure

A standing wave type of microwave linear particle accelerator (40) has a sequence of microwave cavities (42), (43), (44), operated in the standing wave mode, with drift tube conduits (31), (32), (33), between them to permit the passage of a beam of charged particles which are accelerated by the electric fields in each cavity. The first cavity (42) into which the particles enter has a conduit (30) comprising a drift region connected to the particle entrance port (2), outlined by a re-entrant nose (3) extending into the first cavity (42). The drift tube conduit (31) between the first and second cavities (42, 43) has a tapered interior, and the diameter at the upstream end is less than the diameter of the conduit (30) in the re-entrant nose (3) of the first cavity (42). This structure significantly reduces the back bombardment of particles moving backward through the port (2), and increases the efficiency of particle focusing and bunching in the first cavity (42 ).

Linear accelerator with improved input cavity structure and including

A compact, small diameter, standing-wave linear accelerator structure suitable for industrial and medical applications is disclosed. The novel structure utilizes a new type of coupling cavity for Pi/2 mode, standing-wave operation. The coupling cavity fits into the webs between the accelerating cavities substantially within the diameter of the acclerating cavities. This is made possible by keeping the center section of the cavity thin to concentrate the electric field vector at the center of a section of the cavity and by enlarging the ends of a section of the coupling cavity to accommodate the magnetic field vector. This structure offers a significant reduction in overall diameter over the side-coupled, annular ring, and existing coaxial coupled structures, while maintaining a high shunt impedance and large nearest neighbor coupling (high group velocity). A prototype 4 MeV, 36 cm long, S-band accelerator incorporating the new structure has been built and tested.

Small-diameter standing-wave linear accelerator structure

In a resonant chain of coupled cavities such as used in a standing-wave linear particle accelerator it is often desirable to change the field strength in some cavities relative to some others. For example, if the output particle energy of an accelerator is changed by varying the fields of all cavities, the distribution of energies of output particles is disturbed. This distribution is largely controlled by the fields in the first group of cavities traversed by the particle beam. According to the invention, the fields can remain constant in the first group and be varied in following cavities. This is done by varying the distribution of electromagnetic field in one cavity asymmetrically with respect to the preceding and the following cavity. The asymmetric coupling produces different acceleration fields in one part of acceleration structure relative to another part. In an accelerator whose accelerating cavities are coupled via non-interacting side cavities, the different coupling may be produced by making the standing-wave field in one side-cavity asymmetric with respect to its coupling irises.

Variable field coupled cavity resonator circuit

Variable energy selection is accomplished in a side cavity coupled standing wave linear accelerator by shifting the phase of the field in a selected side coupling cavity by .pi. radians where such side coupling cavity is disposed intermediate groups of accelerating cavities. For an average acceleration energy of E.sub.1 (MeV) per interaction cavity, and a total number of N interaction cavities, the total energy gain is E.sub.1 (N-2N.sub.1) where N.sub.1 is the number of interaction cavities traversed beyond the incidence of the phase shift. The phase shift is most simply accomplished by changing the selected side cavity configuration mechanically in repeatable manner so that its resonant excitation is switched from TM.sub.010 mode to either TM.sub.011 or TEM modes. Thus, the total energy gain can be varied without changing the RF input power. In addition, the beam energy spread is unaffected.

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Cupertino, CA, United States of America

Eiji Tanabe